FIELD OF THE INVENTION
The invention relates to a method for common transmission of digital source and control data between data sources and sinks being connected over data lines, which includes transmitting the source and control data in a format specifying a clocked sequence of individual bit groups of equal length, reserving each of certain bit positions in the groups for the source and control data, and forming a coherent region within one bit group from the bit positions reserved for the source data. Through a data line, the source and control data are transferred in a continuous data stream which is synchronous to a clock signal. The clock signal is generated by a single subscriber. All other subscribers synchronize themselves to that clock signal. Purely asynchronous data transmission methods have to be differentiated therefrom as packet or package-oriented data transmission methods, for example ATM-methods.
Methods of that type are used wherever different electrical and electronic devices that are intended to exchange information with one another are linked to one another through the use of data lines in what is sometimes a complicated way. In the audio field, for instance, communication between inter-linked data sources on one hand, such as CD players, radio receivers and cassette tape recorders, and the data sinks connected with them on the other hand, such as amplifier-speaker combinations, can be controlled by such a method.
In the course of development of CD players, the so-called SPDIF format (Sony/Philips Digital Interface Format), which is also known by the designation IEC 958, has become established as the standard. That format prescribes transmission of the data in a frame which includes two subframes or bit groups. Each subframe includes a preamble of four bits for control data, followed by 24 bits for source data and ending with four bits for special control data. One subframe of each frame is assigned to the left audio channel, and the other subframe is assigned to the right audio channel. The rigid layout of that format is disadvantageous, because it is suitable in principle only for the transmission of two channels.